The present invention is one that relates to a method of making composites of metals with their metal oxides using, for example, aluminum and alumina, and bonding these composites with metal or ceramic members.
Prior conventional methods of bonding of metals and metal oxides used appropriate proportions of oxides in the form of flakes, particles and fibers in order to increase the mechanical, chemical and physical properties of the metals with respect to their increased strength and of the metal oxides with respect to their refractory, anti-corrosion and wear resistant properties. The properties of these composites were widely utilized in applications such as cyclone liners, piston engine cams, burner tubes and parts for heating furnaces.
Japanese Patent Publication Hei 3-75508 [1991] described such a method of making such ceramics wherein a ceramic matrix composite is obtained by forming a mother metal oxide ceramic by oxidation reaction of the mother metal, and shaping the mother metal oxide that would be the growth material in the oxide formed as a three dimensional network.
Oxides of such mother metals require introduction of gas phase oxidizers of oxygen or air in order to perform the oxidation reaction. As a result, this method requires a special apparatus for introducing the oxidizers inside the furnace, resulting in escalating equipment costs. Additionally, this method requires smelting furnaces or melt sinks in order to melt the mother metal that is the supply material for growing the composite. Accordingly, they require specialized calcining furnaces, which is turn requires complicated calcining work and work supervision.
A principal drawback of this method in the mother metal cannot bond with metal members during the manufacture of composites because the surfaces of these metal members are oxidized.
Further, there are difficulties in adding metal elements to the composites because the oxygen supply source is air. Thus, composite growth cannot occur in a direction where the preform oxygen supply is shielded and it is necessary to form barriers to prevent composite growth. As a result there is directionality in the preform immersion in the smelting furnace, and it is necessary to, as discussed above to supervise the operation inside the furnace during calcining.